The present invention relates to devices for applying a stopper or cap on the neck of a bottle or similar container, of the type comprising an applying head movable along an axis and provided with an assembly for gripping the cap having a tubular body with an end mouth for receiving and holding the cap, and wherein is slidably mounted an ejector member inside said tubular body along said axis.
A device of the type specified above is disclosed, for instance, in European patent application EP 1 103 513 A1, which refers to a screwing device in which the applying head is provided both with an axial movement, and with a rotary movement for screwing a cap onto the threaded neck of a bottle. In known devices of this kind, an ejector member is provided to eject the cap from the gripping assembly if, for any reason, the operation of applying the cap is not performed and the cap remains caught within the gripping assembly.
A high production rate machine for applying caps on bottles typically has a general carrousel configuration, with a plurality of applying heads which operate moving in synchronism along the carrousel together with the supports for the bottles. While each applying head and the corresponding bottle positioned below it move along the carrousel, the applying head previously loaded with a cap moves downwards and rotates, screwing the cap on the neck of the bottle, then returns to a raised position. Obviously, if the screwing operation is not performed, for example because the bottle is missing, or because of a misaligned positioning of the cap in the gripping assembly of the head, the cap remains in the gripping assembly also during the final phase of re-raising of the head, so it must be eliminated before the head, as the rotation of the carrousel continues, reaches the position where a new cap is picked up to perform a new cycle on a new bottle.
In prior art devices, the ejector member is constituted by a stem element which is mounted axially slidable through the head and which is controlled in its axial position by a respective actuating transmission. For example, in the case of conventional machines, both the axial motion of the head and the axial motion of the ejector stem are obtained by using cam-following rollers, borne by said elements, which roll on cam tracks during the rotation of the carrousel. The provision of an ejector member according to the prior art described above therefore entails a construction complication and it is a source of drawbacks from the standpoint of the compatibility of the machine with the regulations on cleanliness and health to be enforced in the case of certain types of bottles and containers, in relation to their content. The provision of an ejector member slidably guided through the applying head is not advantageous from this point of view, because the ejector member continually moves between the lower area of the head, which must be kept clean and aseptic, and the upper area, which is kept isolated by the lower part because it includes the various actuation mechanisms of the machine and the related lubrication system.